Taking The Mystery Out Of R-410A
These and other reasons caused the Winnipeg Chapter of the Refrigeration Service Engineers Society to offer a daylong seminar on the subject. Some aspects of the presentations were specific to Canada, but much applied to technicians everywhere. The seminar included the basics of refrigeration, as well as the unique aspects of R-410A.
Portions of the program drew upon material from the publication Universal R-410A Safety and Training from ESCO Press.
The EnvironmentMark Miller, executive director of the Manitoba Ozone Protection Industry Association, noted the furor over R-410A is because it is an HFC and therefore “not an ozone depletor,” and the fact that it is “a binary near-azeotrope,” meaning it has only two refrigerants in its blend and little temperature glide. One theme of the conference was the concept that binary is better than ternary (three-refrigerant blends) and the lower the glide, the better.
Like his counterparts in the environmental movement in the United States, Miller is passionate about the need to protect the ozone layer, with the phaseout of CFCs and HCFCs as an important part of that effort.
He said, “The ozone layer is currently at its most vulnerable state and will be for the next 15 years. Severe ozone depletion in the Arctic spring could become more frequent.” Reduction of ozone-depleting substances such as CFCs and HCFCs “may have a positive environmental impact in the future.”
He added, “Given full implementation of the Montreal Protocol by all countries, the ozone layer will recover by the middle of this century.”
The BasicsBotho Kramer, a retired instructor from Red River College in Winnipeg, led attendees through some of the fundamentals of refrigeration and air conditioning, with an emphasis on R-410A. He specifically looked at each component in the refrigeration cycle.
It was noted that manufacturers have redesigned compressors to work with R-410A. Part of the redesign is an increased wall thickness due to higher pressures.
It was also noted that a compressor designed for R-22 should never be used with R-410A. The R-410A compressors have internal pressure relief (IPR) settings that are different than those for R-22. For example, the IPR will open at a pressure of 375 to 450 psig for R-22 systems and a pressure of 550 to 625 psig for R-410A systems. Kramer noted that the suction and discharge pressures are 50 percent to 70 percent greater with R-410A than R-22, but the discharge temperature of R-410A is lower due to its higher vapor heat capacity.
It was noted that R-410A will require a change in the high- and low-pressure switch settings due to increased pressure of the refrigerant.
As far as the condenser is concerned, it was noted that equipment designed for R-22 cannot withstand the higher pressure of R-410A. A condensing unit must be replaced with a specific model designed for R-410A.
Concerning filter-driers, Kramer said such components must have a rated working pressure of no less than 600 psig and must be approved for use with R-410A. And technicians need to check with system manufacturers for specific driers to use.
Kramer did note that liquid lines designed for R-22 can also be used with R-410A “if sized correctly and cleaned properly.”
A major issue concerned metering devices, with Kramer noting that if the same metering device was used in an R-410A system and an R-22 system, it would be oversized in the 410A system, because the higher pressures of 410A systems make for greater refrigerant mass flow rates through the metering device. Kramer said R-410A metering systems are designed to be about 15 percent smaller than those in R-22 systems in order to achieve the same capacity.
One question that arose concerned being able to use the evaporator or indoor coil from an R-22 system when changing out to a 410A air conditioner. It was noted that although some R-22 indoor coils meet the UL-approved design and service pressure rating of 235 psig, a technician should discuss the situation with the manufacturer before using an R-22 indoor coil with R-410A. And Kramer said suction lines used with R-22 can also be used with R-410A, provided they are properly sized and properly cleaned.
The ChemistryIn looking at the chemistry of R-410A, George Kurowski, an instructor at Red River College, began his discussion by noting the widespread use of R-22 may have contributed to its phaseout. While HCFC-22 did not have near the ozone depleting potential of CFCs, it was so widely used that any leakage came from so many places and applications as to raise concern of environmentalists.
“R-22 was its own worst enemy,” he said.
Another issue for contractors to be aware of, he said, is the color of refrigerant containers. R-410A has rose color cylinders while
R-407C cylinders are said to be medium brown. “But I’m seeing variations in this color for 407C, with cylinders that may look tan.”
Much of his talk focused on temperature glides of HFC refrigerants and terminology such as azeotropic, near-azeotropic, and zeotrophic. He noted that R-410A is typically classified as a near-azeotropic. “But because R-410A has a very small temperature glide and fractionation potential, the blend is often referred to as an azeotropic blend. This is because it acts much like a single component or pure compound refrigerant.” By contrast, he said, R-407C has a high temperature glide. “The technician will have to use a pressure/temperature chart and note that there is both a dew point temperature and a bubble point temperature for each pressure value listed for 407C.”
One argument advanced for use of R-407C in place of R-22 is that is does not require a major equipment changeout as does R-410A. But because of issues like glide and efficiencies, Kurowski said, “If an R-22 system is in real trouble, the technician would prefer a total conversion to R-410A rather than a retrofit to 407C.”
He took a look at the tools for R-410A. He said the gauge manifold needs to be specially designed to withstand high pressures. Manifold sets for this application range up to 800 psig on the high side and 250 psig on the low side with a 550 psig low-side retard. Hoses need a service rating of 800 psig. Micron gauges need to be used when evacuating a system to 500 microns, as manifolds will not read the deeper vacuum measurements accurately.
On top of this, Kurowski noted that a 500-micron evacuation will not separate moisture from POE oils in R-410A systems. So, in addition to a 500-micron evacuation, a liquid line filter-drier must be installed and replaced whenever a system is opened.
He did speak favorably of tools, test instruments, and recovery equipment on the market today for use with R-410A. One piece of advice to technicians concerned adding R-410A to a system and making sure it comes out of the charging cylinder as a liquid to avoid any fractionation and for optimum system performance.
An additional consideration concerns the concept of ‘throttle.’ If a service tech wants to add liquid refrigerant to an operating system, it is important to make sure the liquid is throttled, and thus vaporized into the low side of the system to avoid compressor damage. A throttling valve can be used to ensure that liquid is converted to vapor prior to entering the system.
Kurowski’s enthusiasm for HFCs came in part from what he sees as a rapid movement away from R-22 by major manufacturers. He cautioned attendees not to assume supplies will be adequate by relying on secondary — and sometimes questionable — sources of R-22.
“I’m talking about smuggling. If you get involved with that situation, you can be seen as a bandit, a thief, a bad guy. And we don’t need that in our industry.”
Another motive, he said, for moving from HCFCs is what he perceived as pending Canadian legislation designed to crack down on improper practices working with CFCs and HCFCs. Kurowski claimed that in some provinces in Canada there are recertification requirements and legislation “that are enough to make one’s blood run cold.”
The Oil IssueTed Schulz, a technician from Trane Canada, called for “diligence on oil.” He noted polyolester oils (POEs) have become the oils of choice for such HFC refrigerants as R-410A, R-407C, and R-404A. The fact that they are wax-free “gives a lower pour point.” The caution flag goes up, he said, because they “are very hygroscopic,” meaning they will attract and retain moisture easily.
“POEs are big sponges,” he said. “There can never be enough concern about how to handle them.”
He then ticked off special concerns with POE such as:
The Safety FactorBrian Baker, a Winnipeg contractor and an RSES regional director, talked about safety, stressing the need to wear eye protection, to be aware of emergency exits, fire extinguishers, and first aid stations, and to keep work areas clean of debris and free of spilled liquids.
Bill Grywinski, service manager of Trane Canada, reviewed classifications of refrigerants based on flammability and toxicity, noting that most of the refrigerants used throughout the industry have been determined to be nonflammable and nontoxic. He also took the technicians through procedures regarding the Material Safety Data Sheet.
Publication date: 06/02/2003